Control Networks

About the Control Network

The Control Network is a set of reference-points of known geospatial coordinates within Boulder County.

NOTE FROM THE COUNTY SURVEYOR: The survey for these Control Points was performed in 1998-2000. Some of these Control Points have been destroyed. Horizontal Data Information may not be current due to subsequent revisions in federal Geoid models. Because of budgetary limitations, this network is not regularly maintained by Boulder County.

Viewing the Control Network

• View the Control Network with a web mapping application
• Geographic Information Systems (GIS) Downloadable Data

Primary Control Network

Beginning in late 1998, 51 control points, 28 existing and 23 new monuments, were selected to provide a primary control network throughout eastern Boulder County. These points have a maximum spacing of six miles between points.

Aylstra Baker Surveying, Inc., retained by CDOT, observed these points in July and August of 1999 and submitted them to the National Geodetic Survey for bluebooking in early 2000. Datasheets for these points are available to the public under Project ID GPS1454.

The horizontal positional accuracy of the coordinates is within a centimeter and the vertical positional accuracy is approximately 0.5 feet. Details on the project can be reviewed in the
Primary Control Project Report.

Secondary Control Network

Crews from Boulder County and participating BASIC members recovered, marked and described 491 survey positions in eastern Boulder County:

• 406 Public Land Survey System positions (section corners, quarter corners, and centers)
• 9 property or subdivision monuments
• 20 witness corners
• 56 survey monuments

Merrick and Company observed these points in the fall and winter of 1999 and 2000 using GPS Real Time Kinematic (RTK) techniques. The horizontal positional accuracy of the coordinates is estimated at +/- eight centimeters. Vertical accuracy was not included. These coordinates are Geographic Information Systems (GIS) Land Positions, not survey coordinates.

The target points were the universe of aliquot corners on or near paved roads and existing survey control points.

Tertiary Control Network

Over the last several years, a number of cities and other agencies have completed projects which include useful information related to the control project.

There are 215 GIS Land Positions of interest in the project area:

• 128 Public Land Survey System positions (section corners, quarter corners, and centers)
• 87 survey monuments
• 86 city or other positions, later re-observed

Because the observations of these other landpoints were fairly close (RMSE of 0.41 feet) to the other control points, they were included in the project database. A comparison of these points is available.

For more information about the Control Network, contact Boulder County GIS at gisinfo@bouldercounty.gov.